1. Field of the Invention
This invention relates to peeling apparatus and, more particularly, to roller-type shrimp-peeling machinery using an array of segmented roller assemblies to remove shells from shrimp meat.
2. Description of the Related Art
Originally introduced because of the high labor costs of peeling small shrimp by hand, shrimp peeling machines are now widely used in the shrimp processing industry. Roller-type shrimp-peeling machines, in particular, dominate the bulk shrimp peeling industry. U.S. Pat. Nos. 2,778,055, Jan. 22, 1957, and 2,537,355, Jan. 9, 1951, both to Fernand S., James M., and Emile M. Lapeyre, describe the basic structure and principles of operation of roller-type shrimp peelers.
U.S. Pat. No. 2,778,055 shows a peeling machine with a rigid framework supporting the peeling elements. A transverse beam divides the machine into two peeling sections. The upper peeling section extends from a rear wall to the beam; the lower peeling section extends from the beam to the lower front end of the machine. Shell-on shrimp are fed over the rear wall to the upper peeling section. Channels are formed in the upper peeling section by groups, or associations, of five rollers for each channel. The association of rollers includes a power roller forming the base of the channel, two channel-forming rollers flanking and spaced slightly above the power roller, and two small-diameter insert rollers between the power roller and the channel-forming rollers. The power rollers extend the full length of the machine through both the upper and lower peeling sections. The power rollers are supported in the lower peeling section by base idler rollers. All of the rollers incline downwardly from the rear wall to the front end of the machine. The channel-forming rollers and the insert rollers extend only the length of the upper peeling section and are mounted at the rear wall and at the transverse beam. The power rollers and the channel-forming rollers are mounted in fixed locations so that their peripheries are separated a distance slightly less than the diameter of the insert rollers. In this way, the insert rollers, which are not fixedly mounted as are the power and channel-forming rollers, can be forcibly urged by spring pressure into the gaps between the power and channel-forming rollers. The spring pressure provides a tight nip between the insert roller and the power roller. In the lower peeling section, two power rollers and a base idler roller at a lower elevation form an inverted triangular lower peeling channel. The power rollers rotate the base idler roller by frictional contact. The power rollers rotate in alternate directions to force shrimp in the upper peeling section into the nips on one side of the channel and then into the nips on the other side of the channel. The shrimp are unwrapped of their shells in the nips, the shells falling as waste through the gaps between the power roller and the channel-forming rollers. Most of the peeling is effected in the upper peeling section. Shells not removed in the upper peeling section are further subjected to pinching action between the large-diameter power rollers and the base idler roller in each channel of the lower peeling section.
The power rollers and the channel-forming rollers are typically constructed of a metal tube or pipe having a rubber coating. Integral with an end of each roller is a gear mounted on a stub shaft. The stub shafts are supported by bearings in the rear wall of the peeler. A suitable drive mechanism is described in U.S. Pat. No. 3,626,551, Dec. 14, 1971, to J. M. Lapeyre. The mechanism includes a gear rack that meshes with the teeth of the gears of the power and channel-forming rollers. A drive motor, through linkages including a pitman arm and cranks, causes the rack to reciprocate back and forth and the engaged rollers to oscillate in alternating rotational directions.
With use, the rubber coating on the power and channel-forming rollers wears off and the rollers have to be replaced. Because the gear is integral with each roller, it must be disengaged from the rack when the roller is removed. More critically, when a new or refurbished roller is installed in the peeler, the roller must be positioned carefully to make sure that its gear meshes precisely with the rack to avoid backlash and other undesirable properties caused by sloppy gear meshing. Aligning the rollers and meshing their gears properly take a lot of trial and error, making roller replacement a time-consuming task.
Another problem is that shrimp slime and other debris can splash into the exposed gear mechanism at the top of the peeling channels. Fouling and corrosion of the gears can result from such debris and juices. Conversely, grease or other gear lubricants can make their way into the peeling channels. Thus, exposure of the gears to the peeling channels is undesirable.
Because the gear is integral with the roller, other problems arise. As one example, the gear teeth are subject to damage during handling of the heavy rollers because the teeth are exposed at the end. Thus, the rollers must be handled more carefully. Because of the gear, the rollers cannot be stored as compactly either because the gear diameter is greater than the roller diameter. As another example, the rubber is put on the roller in an extrusion process. Because the extruder cannot accommodate the larger diameter of the gear, the extrusion process must be stopped for each roller. The gearless end of the roller must then be backed into the extruder for the entire length of the roller before the extruder is restarted and the roller moves forward and is coated with the rubber layer. Thus, the integral gear is not conducive a faster, continuous extrusion process.